The objective of this project is to identify a humoral satiety factor useful for the treatment of obesity. We have shown that a factor in the plasma of rats with intestinal bypass surgery is capable of decreasing food intake of fasted recipient rats by about 30 percent in the first hour after intraperitoneal injection. This reduction in food intake is almost exactly the same as the difference in intake of bypass and sham bypass rats fasted overnight. We propose to attempt to purify, isolate and identify this humoral satiety factor and to determine its mechanism of action. Plasma from bypass rats will be processed by gel filtration, ultramembrane filtration and by heat and acid degradation. Satiety activity will continue to be assessed by the crude bioassay of measuring food intake of fasted recipient rats after intraperitoneal injection of plasma or plasma fractions, but more sensitive, less expensive methods of assay will be sought. Further studies on the effects of intestinal bypass on meal patterns, intermeal interval and dietary preferences will be carried out in an attempt to determine the mechanism of the decreased food intake after bypass and after injection of humoral satiety factor.